public void StartDownloadAsync(DateTime beginTime, DateTime endTime, string fileName) { NetDvrTime begin = new NetDvrTime { Year = (uint)beginTime.Year, Month = (uint)beginTime.Month, Day = (uint)beginTime.Day, Hour = (uint)beginTime.Hour, Minute = (uint)beginTime.Minute }; NetDvrTime end = new NetDvrTime { Year = (uint)endTime.Year, Month = (uint)endTime.Month, Day = (uint)endTime.Day, Hour = (uint)endTime.Hour, Minute = (uint)endTime.Minute }; NetDvrPlayCondition condition = new NetDvrPlayCondition(); condition.Channel = 33; condition.StartTime = begin; condition.StopTime = end; _fileHandle = OfficalAPI.NET_DVR_GetFileByTime_V40(_userId, fileName, ref condition); PlayBackControl(NetDvrPlayBackControlCode.NET_DVR_PLAYSTART); }